The concept of using geosynthetic clay liners (GCLs) for creating a low permeability layer or barrier for use in landfills and man-made bodies of water is well known. While GCLs made with bentonite provide an effective barrier, users of such GCLs often complain that the GCLs are not effective enough, i.e. the GCLs do not provide sufficiently low permeabilities under certain circumstances, such as landfill caps and deep ponds, because of low confining stresses that can practically be applied to the GCL as a result of soil cover thickness limitations.
For example, many state regulations and project specifications require that the drainage out of a man-made pond be less than 500 gallons per day per acre of pond. This requirement is problematic for deep ponds where the height of the water level is greater than 3 feet. In practice, the drainage out of deep ponds lined with conventional GCLs generally exceeds several thousand gallons per day per acre of pond because current GCLs have permeabilities ranging from 5.times.10.sup.-9 cm/sec to 1.times.10.sup.-7 cm/sec. Further, typical GCLs are relatively thin having a typical thickness of 0.7".
Therefore, it would be desirable to provide a bentonite GCL with an improved or controlled permeability. The resulting GCL could be an ultra low permeability GCL used to provide an effective barrier against the transmission of liquids (i.e. with permeabilities less than 5.times.10.sup.-10 cm/sec).